#include <iostream>
#include <cassert>
#include <cstring>
#include <cerrno>
#include <cstdio>
#include <string>
#include <sys/stat.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <unistd.h>

using namespace std;

#define PATHNAME "."
#define PROJID 0x6667

const int gsize = 4096;

key_t getKey(){
    key_t k = ftok(PATHNAME, PROJID);
    if(k == -1){
        cout << errno << " : " << strerror(errno) << endl;
        exit(1);
    }
    return k;
}

string toHex(int x){
    char buffer[64];
    snprintf(buffer, sizeof(buffer), "0x%x", x);
    return buffer;
}

int shmHelper(key_t k, int size, int flag){
    int shmid = shmget(k, size, flag);
    if(shmid == -1){
        cout << errno << " : " << strerror(errno) << endl;
        exit(2);
    }
    return shmid;
}

int createShm(key_t k, int size){
    umask(0);
    return shmHelper(k, size, IPC_CREAT | IPC_EXCL | 0666);
}

int getShm(key_t k, int size){
    return shmHelper(k, size, IPC_CREAT);
}

char* attachShm(int shmid){
    char* start = (char*)shmat(shmid, nullptr, 0);
    return start;
}

void detachShm(char* start){
    int n = shmdt(start);
    assert(n != -1);
    (void)n;
}

void delShm(int shmid){
    int n = shmctl(shmid, IPC_RMID, nullptr);
    assert(n != -1);
    (void)n;
}

#define SERVER 1
#define CLIENT 0

class Init{
public:
    Init(int t)
    :type(t){
        key_t k = getKey();
        if(type == SERVER)
            shmid = createShm(k, gsize);
        else
            shmid = getShm(k, gsize);
        start = attachShm(shmid);
    }

    char* getStart(){
        return start;
    }

    ~Init(){
        detachShm(start);
        if(type == SERVER)
            delShm(shmid);
    }
private:
    char* start;
    int type;
    int shmid;
};